Numerical simulations of flow patterns and mass exchange processes in dead zones

Contaminants and nutrients transport in streams and rivers is significantly affected by the presence of dead zones that are due to geometrical irregularities, that may have both natural and anthropic origins. Dead zones are characterized by mean flow velocity in the main stream direction approximately equal to zero and by exchange processes of solutes with the main stream. This paper presents the preliminary results of a numerical study undertaken to investigate the fundamental flow phenomena around and inside a simplified geometry, representative of flow in natural rivers with dead zones. Exchange rates between the dead zone and the channel were calculated resulting in a good agreement with previous literature experimental values for the same geometry.